首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   704219篇
  免费   23476篇
  国内免费   11635篇
化学   378316篇
晶体学   9942篇
力学   35274篇
综合类   547篇
数学   94982篇
物理学   220269篇
  2021年   6761篇
  2020年   7882篇
  2019年   7960篇
  2018年   15413篇
  2017年   15879篇
  2016年   15946篇
  2015年   10754篇
  2014年   13783篇
  2013年   30115篇
  2012年   29336篇
  2011年   40109篇
  2010年   25984篇
  2009年   25517篇
  2008年   34021篇
  2007年   36471篇
  2006年   24301篇
  2005年   26956篇
  2004年   21593篇
  2003年   19237篇
  2002年   17169篇
  2001年   17197篇
  2000年   13693篇
  1999年   11318篇
  1998年   9692篇
  1997年   9337篇
  1996年   9500篇
  1995年   8453篇
  1994年   8348篇
  1993年   7618篇
  1992年   8348篇
  1991年   8153篇
  1990年   7714篇
  1989年   7192篇
  1988年   7450篇
  1987年   7003篇
  1986年   6712篇
  1985年   9162篇
  1984年   9383篇
  1983年   7705篇
  1982年   8168篇
  1981年   8091篇
  1980年   7823篇
  1979年   7902篇
  1978年   8196篇
  1977年   8057篇
  1976年   8109篇
  1975年   7721篇
  1974年   7625篇
  1973年   7951篇
  1972年   5096篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Sun  Qinqin  Wang  Xiuye  Yang  Guolai  Chen  Ye-Hwa  Ma  Fai 《Nonlinear dynamics》2022,109(3):1629-1650
Nonlinear Dynamics - This paper proposes an optimal parameter design of control scheme for mechanical systems by adopting the Stackelberg game theory. The goal of the control is to drive the...  相似文献   
52.
Wang  Xigui  Ruan  Jiafu  Wang  Yongmei  Ji  Shue  An  Siyuan 《Meccanica》2021,56(2):303-316
Meccanica - In gear pair actual alternating meshing process, the comprehensive errors of the transmission system and the thermal elastic deformation of the teeth body cause the gears in the meshing...  相似文献   
53.
Annals of the Institute of Statistical Mathematics - In this paper, a model averaging approach is developed for the linear regression models with response missing at random. It is shown that the...  相似文献   
54.
Chen  R. J.  Chen  W.  Kong  F. L. 《Analysis Mathematica》2022,48(1):19-28

Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.

  相似文献   
55.
Physics of the Solid State - The external factors which influence the ferromagnetic resonance (FMR) line width in bilayer (ferromagnet/antiferromagnet) exchange-biased systems are studied. The...  相似文献   
56.
Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst.  相似文献   
57.
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that...  相似文献   
58.
The chiral phase transition and equation of state are studied within a novel self-consistent mean-field approximation of the two-flavor Nambu-Jona-Lasinio model. In this newly developed model, modifications to the chemical μ and chiral chemical \begin{document}$\mu_5$\end{document} potentials are naturally included by introducing vector and axial-vector channels from Fierz-transformed Lagrangian to the standard Lagrangian. In the proper-time scheme, the chiral phase transition is a crossover in the \begin{document}$T-\mu$\end{document} plane. However, when \begin{document}$\mu_5$\end{document} is incorporated, our study demonstrates that a first order phase transition may emerge. Furthermore, the chiral imbalance will soften the equation of state of quark matter. The mass-radius relationship and tidal deformability of quark stars are calculated. The maximum mass and radius decrease as \begin{document}$\mu_5$\end{document} increases. Our study also indicates that the vector and axial-vector channels exhibit an opposite influence on the equation of state.  相似文献   
59.
Crystallography Reports - The specific features of the formation of crystallites in gallium arsenide crystals grown by the Czochralski method have been investigated. The crystallites are found to...  相似文献   
60.
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号